Grand Cherokee's rough idle may be from outdated PCM software

Some 2002-04 Jeep Grand Cherokees with 4.7-liter engines can produce a rough idle when at a stop, with the transmission in gear and the engine at normal operating temperature. FCA L.L.C. says if the check-engine light is off when the rough idle occurs and there are no trouble codes stored, the PCM is in need of updated software. Check with a dealer for the application specifics of the reprogramming job.

"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected].

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